The pediatric syndrome of sleep disordered breathing (SDB) encompasses children with simple snoring, obstructive hypoventilation (OH), and varying degrees of obstructive sleep apnea (OSA). The syndrome occurs in more than 12% of all children, with most falling within the mild to moderate range of the severity spectrum. Although the long-term cardiovascular sequelae of severe SDB are well recognized, those that develop secondary to milder forms of SDB remain undefined. The lack of knowledge regarding the long-term cardiovascular morbidity of less severe forms of SDB precludes adequate management of children with the disorder and prevention of cardiovascular disease during adulthood. We build on intriguing preliminary data demonstrating for the first time that compared to controls, lean and obese children with SDB have structural and functional changes of the carotid artery, higher systolic blood pressure and wider pulse pressure. All are important indicators of blood vessel stiffness and determinants of left ventricular load and mass. The goals of this study are threefold: 1) to compare inflammatory cardiovascular disease mechanisms in 5- to 13-year-old children with varying degrees of SDB to those in normal controls; 2) to determine how cytokine levels in plasma relate to those in tonsils; 3) to examine the relationship between inflammatory markers and prognostically important cardiovascular measures such as carotid intima thickness, carotid compliance, pulse pressure, aortic stiffness and left ventricular mass and function before and after adenotonsillectomy. As an important segment of this K 24 application, this research will serve as a platform for the mentees in the program.